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Thu, 2 Jul 2020 14:28:58 +0000 (UTC) Subject: Re: [PATCH v9 28/34] qcow2: Add subcluster support to qcow2_co_pwrite_zeroes() To: Alberto Garcia , qemu-devel@nongnu.org References: <3c6140626c443f1eb443881eddcfb65b6107aff2.1593342067.git.berto@igalia.com> From: Max Reitz Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: <25384933-0ca3-3f50-c1af-4c92e8c88328@redhat.com> Date: Thu, 2 Jul 2020 16:28:57 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <3c6140626c443f1eb443881eddcfb65b6107aff2.1593342067.git.berto@igalia.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="sq5xbjMnO6yPPrnYUR83tP3lHHMC9qABT" Received-SPF: pass client-ip=207.211.31.81; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/02 04:18:28 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Derek Su , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --sq5xbjMnO6yPPrnYUR83tP3lHHMC9qABT Content-Type: multipart/mixed; boundary="AJQogpYMhWN1CtMfn5glg1AdRRgCOf8Ih" --AJQogpYMhWN1CtMfn5glg1AdRRgCOf8Ih Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 28.06.20 13:02, Alberto Garcia wrote: > This works now at the subcluster level and pwrite_zeroes_alignment is > updated accordingly. >=20 > qcow2_cluster_zeroize() is turned into qcow2_subcluster_zeroize() with > the following changes: >=20 > - The request can now be subcluster-aligned. >=20 > - The cluster-aligned body of the request is still zeroized using > zero_in_l2_slice() as before. >=20 > - The subcluster-aligned head and tail of the request are zeroized > with the new zero_l2_subclusters() function. >=20 > There is just one thing to take into account for a possible future > improvement: compressed clusters cannot be partially zeroized so > zero_l2_subclusters() on the head or the tail can return -ENOTSUP. > This makes the caller repeat the *complete* request and write actual > zeroes to disk. This is sub-optimal because >=20 > 1) if the head area was compressed we would still be able to use > the fast path for the body and possibly the tail. >=20 > 2) if the tail area was compressed we are writing zeroes to the > head and the body areas, which are already zeroized. >=20 > Signed-off-by: Alberto Garcia > Reviewed-by: Eric Blake > --- > block/qcow2.h | 4 +-- > block/qcow2-cluster.c | 80 +++++++++++++++++++++++++++++++++++++++---- > block/qcow2.c | 27 ++++++++------- > 3 files changed, 90 insertions(+), 21 deletions(-) [...] > diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c > index deff838fe8..1641976028 100644 > --- a/block/qcow2-cluster.c > +++ b/block/qcow2-cluster.c > @@ -2015,12 +2015,58 @@ static int zero_in_l2_slice(BlockDriverState *bs,= uint64_t offset, > return nb_clusters; > } > =20 > -int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset, > - uint64_t bytes, int flags) > +static int zero_l2_subclusters(BlockDriverState *bs, uint64_t offset, > + unsigned nb_subclusters) > +{ > + BDRVQcow2State *s =3D bs->opaque; > + uint64_t *l2_slice; > + uint64_t old_l2_bitmap, l2_bitmap; > + int l2_index, ret, sc =3D offset_to_sc_index(s, offset); > + > + /* For full clusters use zero_in_l2_slice() instead */ > + assert(nb_subclusters > 0 && nb_subclusters < s->subclusters_per_clu= ster); > + assert(sc + nb_subclusters <=3D s->subclusters_per_cluster); Maybe we should also assert that @offset is aligned to the subcluster size. [...] > diff --git a/block/qcow2.c b/block/qcow2.c > index 86258fbc22..4edc3c72b9 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c [...] > @@ -4367,12 +4367,13 @@ static int coroutine_fn qcow2_co_truncate(BlockDr= iverState *bs, int64_t offset, > uint64_t zero_start =3D QEMU_ALIGN_UP(old_length, s->cluster_siz= e); Can we instead align this to just subclusters? > =20 > /* > - * Use zero clusters as much as we can. qcow2_cluster_zeroize() > + * Use zero clusters as much as we can. qcow2_subcluster_zeroize= () > * requires a cluster-aligned start. The end may be unaligned if= it is s/cluster/subcluster/? Max > * at the end of the image (which it is here). > */ > if (offset > zero_start) { > - ret =3D qcow2_cluster_zeroize(bs, zero_start, offset - zero_= start, 0); > + ret =3D qcow2_subcluster_zeroize(bs, zero_start, offset - ze= ro_start, > + 0); > if (ret < 0) { > error_setg_errno(errp, -ret, "Failed to zero out new clu= sters"); > goto fail; >=20 --AJQogpYMhWN1CtMfn5glg1AdRRgCOf8Ih-- --sq5xbjMnO6yPPrnYUR83tP3lHHMC9qABT Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl797ykACgkQ9AfbAGHV z0B/KAgAnJs3K3v9bfYpwLzhiFWiUotFJRF0GlNxRxRK/B/CmFGUPyYMeMrLGCs2 ixTluaG0/So3eH/rINaCKYiTmOBijc0RZ+aj+Hu7K75IZ3SjmQVt58OLZeOk3m2L wLTHZCTOdSP68fQfz6a0PUVKHLjp4uj8jMKYsZGTmADkHK9wi3Hr6msnck4lzCAF BlMW7acGP+7GTfUNocx2eehjbCtIsAPUYUqrtVhqsHjKz8xaitxUFSOQdix3+SIA mTqsfOLlW0i95wpHJ3RWnJ/ds9YVfk6Z6syP4+cUtrcU1gVCTp7BP5G8h1VyE+g0 DH1gvI3w+mfIsA7xEVbWSvuDSXNmpQ== =NLRj -----END PGP SIGNATURE----- --sq5xbjMnO6yPPrnYUR83tP3lHHMC9qABT--